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A few days ago, a pound of "Sil-Fos 15" brazing wire arrived. Today, I finally found some time to play with it. It turns out that I already had a roll of 3/8" ACR tubing laying around in the garage ( long story ).

Lacking any connectors, I chopped off a couple of pieces of tubing ( waiting on a quality tubing cutter to come in the mail ). Cleaned them off, butted one to the other, and brazed them together. I have to say, it was a piece of cake. I set up my O/A torch for a nice little 1/4" neutral flame, heated the copper red hot, touched the brazing rod to it - and it just flowed. No fuss, no muss. A perfect-looking joint resulted. Visibly I would say "that ain't gonna leak". And it seems to be just as strong as the rest of the tubing. Need to get some unions to try out. Also need some real emery cloth - I used a metal cleaning buff on my Dremel.

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Out in the field I try to avoid getting the pipe red hot and glowing. On the 3/8 its almost impossible. When the copper gets red hot it reacts with the oxygen in the air and oxidizes the copper. The black flakes you see on the outside of the pipe are also on the inside. These flakes clog up sceeens, txv's and driers. By flowing nitrogen through the pipe you will avoid oxidation.

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*** So it doesn't HAVE to be red hot to flow the Sil-Fos? That's kind
of how it seemed, but I wasn't sure. Other data I've seen on the Web intimated that it needed to be red hot.

Quote:

Originally Posted by Master of Cold

On the 3/8 its almost impossible.

*** Sounds like an excuse to buy a Meco torch

Quote:

Originally Posted by Master of Cold

When the copper gets red hot it reacts with the oxygen in the air and oxidizes the copper. The black flakes you see on the outside of the pipe are also on the inside. These flakes clog up sceeens, txv's and driers. By flowing nitrogen through the pipe you will avoid oxidation.

According to the Sil-Fos website, Sil-fos 15 melts at 1190F but does not
"flow" until 1475F. It seems to me that you need "flow" to get capillary
action - otherwise, sealing is mostly on the surface of the joint.